Why does Blender seem to freeze when I run this script?
Blender freezes because it's running the script and rendering out the frames. If you look at the System Console (Window -> Toggle System Console) while it runs, you will see the frame numbers and the filepath listed as each frame is rendered.

The amount of frames rendered depends on your Frame Range. By default this is set to 250 frames. Since the script renders out frames 8 times, this would be a total of 2000 frames. Blender will be frozen while this runs, which could take a few minutes depending on your scene and system specs.